1. Field of the Invention
The present invention relates generally to exhaust heat recovery systems for motor vehicles and, more specifically, to an exhaust valve for a combustion engine in a motor vehicle.
2. Description of the Related Art
It is known to provide a supplemental heating device such as an exhaust heat recovery system for a motor vehicle to harness waste heat from exhaust gases to heat air for an occupant compartment of the motor vehicle. Generally, the exhaust heat recovery system includes an exhaust pipe mounted to an exit end of a catalytic converter of an exhaust system of the motor vehicle and a heat exchanger mounted to and in parallel with the exhaust pipe. The exhaust heat recovery system also includes a by-pass valve to control the flow of exhaust gases from the catalytic converter through either the exhaust pipe or the heat exchanger. The exhaust heat recovery system includes a back-pressure valve in series with the heat exchanger to prevent exhaust gases from re-entering the heat exchanger and provides back pressure against an engine of the motor vehicle to load the engine to reject more heat. The exhaust heat recovery system further includes an inlet and an outlet connected to the heat exchanger to allow coolant to flow therethrough to provide additional heat.
The by-pass valve is of a butterfly plate type to provide sealing against exhaust gases during a backpressure mode of the exhaust heat recovery system. The exhaust by-pass valve must divert all exhaust gases through the heat exchanger and ensure that a leakfree environment is maintained while under backpressure. However, current exhaust by-pass valves include machined xe2x80x9cface sealsxe2x80x9d on a valve housing for the butterfly plate to seal against and high force springs on a valve shaft to promote good sealing of the butterfly plate against xe2x80x9cbushingxe2x80x9d leakage. The current exhaust by-pass valves have high torque requirements provided by an actuator for sealing the butterfly plate on the face seal, gaps between the butterfly plate and valve housing for thermal expansion and thin walls on the valve housing to avoid welding distortions.
Although the above exhaust by-pass valves have worked, they suffer from the disadvantage that they have a relatively large leak rate, which is undesired. Another disadvantage of the exhaust by-pass valves is that high tolerance machining is required for both face sealing and the bushings. Yet another disadvantage of the exhaust by-pass valves is that the exhaust by-pass valve may not seal well due to holes near ends of the shaft. Still another disadvantage of the exhaust by-pass valves is that, after thermal cycling, vibration cycling, soot-build up and corrosion, the valve has the potential to loose its leak performance. A further disadvantage of the exhaust by-pass valves is that they require a reaming process in the hole for the butterfly plate and there are many components. Therefore, there is a need in the art to provide an exhaust by-pass valve for an exhaust heat recovery system in a motor vehicle, which overcomes these disadvantages.
Accordingly, the present invention is an exhaust valve including a housing having a passageway extending axially therethrough. The exhaust valve also includes a rotatable butterfly plate disposed in the passageway of the housing and having an annular groove in a periphery thereof. The exhaust valve further includes a ring seal disposed in the groove. The ring seal is radially compressible and expandable for engagement and disengagement with the housing for opening and closing the passageway to allow and prevent exhaust gases flowing therethrough.
One advantage of the present invention is that a new exhaust valve is provided for a combustion engine in a motor vehicle. Another advantage of the present invention is that the exhaust valve eliminates bearing/bushing leakage under backpressure. Yet another advantage of the present invention is that the exhaust valve incorporates a xe2x80x9cring sealxe2x80x9d in the butterfly plate. Still another advantage of the present invention is that the exhaust valve has a shaft and bushings for the shaft disposed after the ring seal and perpendicular with the butterfly plate. A further advantage of the present invention is that the exhaust valve provides better exhaust sealing performance under backpressure for an exhaust heat recovery system at a reduced manufacturing cost. Yet a further advantage of the present invention is that the exhaust valve improves emissions, windscreen defrosting time, occupant comfort and overall operator satisfaction.